Plasma generating devices may be used for a variety of purposes such as plasma etching, deposition/coating, cleaning and the like to manufacture or further process various products such as printed circuit boards (PCB) or a printed wire boards (PWB). These devices may generate their plasma fields by applying an electromagnetic radiation (e.g., for many plasma applications, this electromagnetic radiation could emanate at a Radio Frequency or RF of 13.56 MHz, although other frequency electromagnetic radiation may be used for other plasma applications) to an internal environment handled by the device. If the device's internal environment further contains a gas (e.g., fluorine, oxygen, chlorine, or the like) then the emitted electromagnetic radiation may then place the atoms of said gas into a highly energized state that splits those atoms into electrons and ions that may then react with the atoms/molecules of the material (e.g., the specimen) to be altered by the plasma field. By controlling the various plasma field generation parameters such as RF power, chamber pressure, gas flow, temperature, exposure time, and the like, various useful changes can be imposed by plasma field upon the specimen (e.g., an etching action.)
One version of a plasma generating device could be a plasma etching device generally comprising a door and a set of walls that generally form a substantially airtight plasma reactor chamber with a hollow interior. The hollow interior for this version could also contain a plurality of RF electrodes that could be powered by electromagnetic radiation (e.g., RF) generation system. The plasma reactor chamber could be further vented by a vacuum system and filled by a gas system. All of these systems could be controlled by appropriate electronics/software (e.g., electronic controller) utilizing operator interface controls (e.g., a control panel.) These various systems could be structurally supported by the device's housing.
The RF electrodes could be plate-shaped and be arranged in a horizontally stacked set. Within this set, the RF electrodes could be spaced apart from one another, alternating between power and ground RF electrodes. These electrodes could further act as support or shelving that could hold several specimens (e.g., PCBs or the like) in a manner that each specimen is singularly being held between a ground electrode and a power electrode.
When such a plasma generating device is used for a coating function, which demands less precision than plasma etching action, a fluid environment may be substituted for the gas environment although a gas environment may be used for the coating function. In this coating function, the electrode-generated electromagnetic field may then create from the liquid/gas present in the plasma reactor chamber a precipitation that is subsequently deposited upon a specimen as a coating (e.g. resulting in a generally protective encapsulation of PCB/PWB.)
The plasma generating devices could be also used within various PCB/PWB manufacturing processes. First step could be the forming a laminate made from copper conduction layers sandwiched between non-conductive layers. Holes (e.g., Pass Through Holes or PTH) could then be drilled laterally through the laminate to substantially provide the boards' electrical connections. After a series of subsequent intermediate processes, the plasma generating devices could then be used to clean (e.g., dcsmear) and then plate (e.g., etched back) the drilled holes.
Such plasma actions could start with a specimen being substantially placed in between (e.g., sandwiched by) a power RF electrode and a ground RF electrode with the plasma reactor chamber then being closed and otherwise sealed. A vacuum could then be induced to remove an outside/ambient atmosphere from the plasma reactor chamber's hollow interior. A plasma forming gas (e.g., chlorine, fluorine, oxygen, etc.) or liquid (for coating action) could then be introduced into the plasma reactor chamber's hollow interior. The RF electrodes within the hollow interior may then energized to generate an electromagnetic field (e.g., radio frequency-based) to create the plasma field. The plasma field could then act upon the specimen to provide the desired plasma type action (e.g., etching, desmearing, etc.)
When the desired plasma action is deemed suitably completed, the RF electrodes may be de-energized; the liquid/gas environment may be removed from the hollow interior; and the outside/ambient atmosphere could be reintroduced into the hollow interior. The plasma reactor chamber may then be unsealed and the processed specimen(s) may be removed from the hollow interior allowing the plasma device to process additional specimens.
Plasma etching devices that process several specimens at the same time utilizing stacked, spaced-apart RF electrodes may encounter a variety of issues regarding the plasma field generation. If a constant and uniform plasma field generation does not occur then uneven etching may result (e.g., “undercooking” some specimens while “overcooking” other specimens; and/or having some portions of one specimen being “undercooked” while remaining portions are “overcooked”.) Such impaired plasma field generation may be caused by the general difficulty in controlling RF electromagnetic emissions for plasma generation (e.g., the electrodes are basically acting like antennas); having the RF electromagnetic field unwantedly grounding out at other points in the plasma reactor chamber besides at the electrodes; and other factors.
What might be needed is a plasma generating device whose plasma reactor chamber that allows one or more specimens to be moved proximate to RF electrode(s) and to be moved through the created plasma field. This specimen movement could allow more energy to be applied to the RF electrodes; possibly cause a reduction in the grounding effect; possibly increase control over the RF electromagnetic field with a general result of greater stability and uniformity in the plasma field generation.
This solution may further allow a definite amount of polytetrafluoroethylene placed proximate to one or more RF electrodes to emit or otherwise generate a sufficient amount of plasma formation gas thus possibly providing a green effect that could reduce the need for separately introducing additional plasma formation gas into the plasma reactor chamber.